Iontophoresis is generally defined as the migration of ions when an electrical current is passed through a solution containing ionized species. The ionized species is usually the ionic form of a drug. The migration of the drug is generally from an iontophoretic system reservoir toward the skin of a patient, and is usually initiated by a small current. Therefore, the most common description of iontophoresis is the delivery of drugs to a patient by the application of electricity.
Iontophoresis provides a noninvasive drug delivery means. When compared to drug delivery by means of a needle, iontophoresis can minimize trauma, pain, infection, and damage.
The primary features of an iontophoresis unit include a battery, a drug reservoir, an indifferent electrolyte reservoir, and usually two electrodes (sometimes referred to as current distribution members which are in contact with the reservoirs). The iontophoresis unit is typically secured to a patient's skin by a fastening means which can include a strap or adhesive means such as adhesive gels. Electrodes are described in a variety of ways but generally include an active electrode and an indifferent electrode. Sometimes the term reservoir system is used to describe an electrode (e.g., reservoir plus electrode). The active electrode has the same charge as the drug to be delivered and the indifferent electrode (also referred to as the return electrode) has a charge opposite the drug to be delivered. For example, if the drug to be delivered to the patient has a positive charge, then the positive electrode will be the active electrode and the negative electrode will serve to complete the circuit. If the drug to be delivered has a negative charge, then the negative electrode will be the active electrode and the positive electrode will be the indifferent electrode. Generally, this can be referred to as a cathode (negative terminal) and anode (positive terminal) electrode system. It is the movement of ions from one electrode to the other electrode that results in the drug being delivered into and through a patient's skin.
Various improvements in iontophoretic methods and devices have been made in the recent past. In particular, many advances have been made in the use and composition of electrodes for iontophoresis. For example, Lattin, U.S. Pat. No. 4,406,658 describes a device in which the polarity of electrodes is reversible. The patent describes an iontophoretic device that permits the iontophoretic process to take place under both electrodes with one application by having a means for switching the polarity of the electrodes. Ellis, U.S. Pat. No. 4,019,510 describes a method for applying low intensity direct current (LIDC) without the detrimental effect of electrical polarization. Another patent, Jacobsen, U.S. Pat. No. 4,886,489, describes a flow through electrode that provides a fresh supply of medicament while taking away the old supply.
In addition, Phipps, U.S. Pat. No. 4,747,819 and Phipps, U.S. Pat. No. 4,744,787 describe improved iontophoretic delivery methods and improved iontophoretic delivery devices, respectively. However, both patents are directed toward teaching how to avoid pH changes and resultant burns to a patient while also increasing drug delivery efficiency. Petelenz, U.S. Pat. No. 4,752,285 also describes methods and devices for iontophoresis which are directed toward avoiding production of competing ions which results in increased efficiency of drug delivery and prevents changes in pH which result in burns to the patient.
However, other than simple replacement, no description or teaching of a device or method for renewing electrodes during iontophoresis has been described.